silencer below 100db ?

Rune

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It seems that more and more tracks have limited the noise to max 100db . With the limited room in a gt40 this is a challenge , at least for me it is. I have made some mufflers just as a test from simple steel sheets I have been able to come close to 100db , but the restriction inside is I belive, way to big . So is there a way to build a silencer that handle 100db with a size one can deal with?
When You see all these new nice gt40s on this forum , with mufflers bougth from shops that sell them . Does they match the noise limit ? or is the noise limit on a track not a issue?
I would like to see pictures of exhaust systems that keep the noise on 100db rpm 4500 and measured three feet from exhaust and 45 deg off.
I use supertrapp without anything to restrict the flow , and the sound is 114 db , and I love it .
But I need to have something else for the track.
I belive that many of you out there have the same challenge.

Rune
 

Randy V

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It can be done, but there are so many variables that there is not a one-size-its-all solution.

Displacement
Camshaft overlap
Compression
Power adders
Primary tube length
Collector length
Primary to collector organization
Header material
RPM range
Et al...

I did see and photograph a design that an ALMS team did in conjunction with Porsche but I have looked for the last few years on my various computers and so far cannot find.
The system was made entirely from inconel and a work of art. The engine reached 8500 RPM and the db readings I saw posted were never over 98 dB.

I wish I could find those pictures.. If nothing else, I will try and sketch the system as I remember it from 11 years ago..
 
Order a set of "LS powers" GD-T70 silencers, they are amazingly silent. the cars have GM LS based engines breathing through 4 to 1 headers and with only the silenser on it it'll go through european approval. it's a straight trhough damper and I don;t know how they got it working so well.

grtz Thomas
 
good idea, they do sound good indeed, guess this tuned one has also such items.

[ame=http://www.youtube.com/watch?v=jtXCR_TZEPs]Heuvelklim Teuven 2009, T70 spyder - YouTube[/ame]
 
My recollection is Frank at Wealden in the UK has developed something suitable - pretty sure they've been written about here before
 
yesterday I came across some Ultima GTR articles and remembered a thread on PH (pistonheads) were they talked about some new and very good sort? silencers that are not so loud? see if I can find that...

found it, they had 2 updates...one in 2008 and one in 2011, don't know if there is room enough for the GT40 though...

anyways...both systems are on this page>>

FACTORY PART UPDATES
 

Randy V

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I have a pair of these on my F5000 but alas i havnt tried them as yet, but they came reccomended from an expat living in the states who has them on his sprint car.
NEW SCHOENFELD MUFFLER,11",SPRINT CAR,MAXIM,J&J,XXX,JEI | eBay

Cheers John

The Schoenfeld mufflers are a straight through design that only (& I mean barely) clips the very peak of the exhaust notes.
I would use either Lobak or Moroso Spiral Flow mufflers before I would choose the Schoenfelds for any operation on public roadways.. They do a much better job.
I haven't given up totally on finding those pics I took 11 years ago at an ALMS race..
 
seeing it again I remember, sadly no soundclip before and after with that system...
the way it suppose to work sounds very good without padding, that way you don't need to repack the muffler after so many miles.

edit...found 2 video's on U-tube, will post them in that thread :D
 
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Ian Anderson

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I also wonder if making those U shaped pipes in that silencer out of perforated tube would make much difference thereby breaking up the pulses even more? Perforated tube open ended or even with a stop on the end so the gas has to flow through the small holes

Perhaps erforated tube for the 2 straight portions and a solid curve as this is so close to the outlets????

Just mre ideas for the noise problem

Ian
 
I guess that brakes the effect of the V shaped obstacles forcing the exhaust gasses going through the labyrinth

edit: reading more about the panel system mufflers, it could mean you get to much resistance pressure which could lead to a heater engine...which is not good.
a abortion muffler (straight through) would always be better in theories that is...
but I guess thats the difficult part when having not many/long pipes in the GT40, I guess thats why some builders use those complicated straight through systems with some U turns so they can ad more mufflers or cats in the system.

attachment.php


for a straight through system it works indeed.

in my Hartge V8 I have made something (in the rear of the end muffler) for noise limit track-days out of aluminium perforated tube, because its in the back-end of the exhaust the gasses are not that hot anymore and the soft material (compared to hard stainless steel) softens the sharp noise and makes the sound even more smooth and nicer...so that works indeed.
 
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I guess that brakes the effect of the V shaped obstacles forcing the exhaust gasses going through the labyrinth

edit: reading more about the panel system mufflers, it could mean you get to much resistance pressure which could lead to a heater engine...which is not good.
a abortion muffler (straight through) would always be better in theories that is...
but I guess thats the difficult part when having not many/long pipes in the GT40, I guess thats why some builders use those complicated straight through systems with some U turns so they can ad more mufflers or cats in the system.

attachment.php


for a straight through system it works indeed.

in my Hartge V8 I have made something (in the rear of the end muffler) for noise limit track-days out of aluminium perforated tube, because its in the back-end of the exhaust the gasses are not that hot anymore and the soft material (compared to hard stainless steel) softens the sharp noise and makes the sound even more smooth and nicer...so that works indeed.

The muffler pictured above is from Russ Nobles car..., not sure what noise levels were, but it was/is very quiet, I also built a similar item for the TVR that has been checked @ 89db [ at full throttle ], no evidence of any overheating issues in the past seven[7] years of racing... TVR one is twin inlet/single tailpipe, sounds very exotic for want of a better term, [ a lot less expensive than a flat plane crank :thumbsup:] & since it finish's usually in the top end of the field I can assure you there is no real power loss.
Only real problem is they are DIY only, not available like that commercially..
 
I should have added to answer Ian's question...drilling perforations in the two enclosed tailpipes will not help in this case as it confuses the length of the tailpipe, the whole idea of constructing the muffler for Russ in this manner was to acheive two things.
1. get the appropriate tailpipe length to suit his engines requirements.
2. keep the noise level down to below track requirements.
From what I understand it acheived both those aims, only down side being its final weight which can be reduced considerably in this case... I know the one on the TVR doesnt weigh much more than 10 or so kg.

Doesnt seem to matter what type of engine I build them for, they have all checked out within db limits for our tracks, in fact when one fitted to a Holden HQ 6 cyl 'fell off' during a race the the car immediately lost power [ even though the rest of the header system was intact ] & was black flagged.
 
Is there any picture of this muffler for the next fabrication step. don´t get the idea how the gases exhaust finaly. And would it make sense to completly separate both sides for beeing closer to the original sound structure ?

Edit:
never mind just found all the answers on the forum in the linked thread above

thanks
TOM
 
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Ian Anderson

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Thanks Jac

I know very little about construction of exhausts and was just putting an idea forward

I think I will attempt to get one made to this design for the Ford motor I am working on that will replace the Morgan lump currently in the car

Ian
 
good to hear its a good system Jac,
so it also flows enough not to disturb it to much to cause to much back pressure.
I had that for a while when my race kats failed and blocked the exhaust flow a bit, normally I did not noticed it to much, but when occasionally on a track or pushing real hard on the German Autobahn, once a year with some friends, I noticed a faster, getting hot engine and power-loss...
I changed a lot to find that problem but couldn't tackle it, then much later I discovered the faulty cats when noticing some little pieces of titanium kat parts in the back of the pipe...

ok, thanks for the input, then I save the pictures of those special mufflers, the great thing about those is the "simplicity" not needing any padding inside which blows out over the years, so no need to repack them. :D
 
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nah Rene, Jan's green/orange GD T70 was running straight pipes at Teuven the noise was indeed amazing. he ponly ran the Cat's on those hillclimb runs. a tad below 700hp as he told me.

on the stock GD silencers you can hardly hear a stock ls1 even at full song it's very very silent, someone payed some good attention to this silencer design.

Btw: if the padding is good and the internal design is ok, there's no need for the padding to come out. altough some dampers are know for doing this right out of the box..... I never had it happen on any cars I worked on.

almost any of the sharpness in noise is made at the tip of the tailpipe btw, think how a trumpet really works

Grtz thomas
 
I thought that sound (in the video at least) was not that loud for such machine.
but if you say the normal GD T70 system is way better, more silent I'm curious...

do you (Thomas) have a video of such system and such car? are those systems trackday freindly in our country? say under 95db? that would be nice...

and indeed the last piece (tip) of the exhaust is very important, a put a thin pipe on or a thick pipe...ore the last tip with perforated material inside, I made such Item in aluminium which is soft and softens the sharp sound a bit when needed on a track.
 
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